Conventionally, as shown in FIGS. 40 to 42, the membrane module of this type includes, for example, a plurality of filtration membranes 11 having an elongated tubular shape, holding members 12 and 13 for holding both ends of the filtration membranes 11, and a reinforcing frame 14 having the holding members 12 and 13 attached thereto for reinforcement. Inside the holding member 12, a water collecting space 16 is formed in which permeate having permeated through the filtration membranes 11 is collected. In the holding member 12 on one side, a water collecting nozzle 18 communicating with the water collecting space 16 is provided. The water collecting nozzle 18 projects to the outer side of the holding member 12.
In the reinforcing frame 14, coupling portions 17 for coupling membrane modules 15 adjacent to each other in the up-down direction are provided. The coupling portions 17 include projections 17a provided in the upper part of the reinforcing frame 14 and recesses 17b provided in the lower part of the reinforcing frame 14.
A membrane cassette 19 is formed by stacking the plurality of membrane modules 15 in the up-down direction. The membrane cassette 19 is immersed in a treatment tank 20. The water collecting nozzle 18 of each of the membrane modules 15 is connected to a suction pipe 21 for sucking permeate (filtrate). A suction pump 22 is connected to the downstream side of the suction pipe 21.
Therefore, when the plurality of membrane modules 15 are stacked in an up-down direction A, the upper membrane module 15 is coupled to the lower membrane module 15 by fitting the projection 17a of the lower membrane module 15 in the recess 17b of the upper membrane module 15. It is possible to prevent the upper membrane module 15 from disengaging from the lower membrane module 15 in a front-rear direction B or a left-right direction C.
Permeate having permeated from the outer sides to the inner sides of the filtration membranes 11 is collected in the water collecting space 16, flows from the water collecting space 16 to the suction pipe 21 through the water collecting nozzle 18, and is extracted to the outside of the treatment tank 20.
The membrane module 15 is described in Japanese Patent Application Laid-Open No. H02-86818.